Mechanical lead pencil



MECHANICAL LEAD PENC IL Filed Jan. 29, 1968 FIG. 1

INVENTOR M Mm MMAM ATTORNEY United States Patent 3,477,791 MECHANICAL LEAD PENCIL N agahiro Yamashita, Tokyo, Japan, assignor to Dai Nihon Bungu Kabushiki Kaisha (trading as The Japan Stationery Co., Ltd.), Tokyo, Japan, a corporate body of Japan Filed Jan. 29, 1968, Ser. No. 701,434 Int. Cl. B43k 21/10 US Cl. 401-64 1 Claim ABSTRACT OF THE DISCLOSURE A mechanical lead pencil includes a device for entirely expelling the lead. It is capable of propelling a pushing rod which fits within a conveying pipe. Both the pushing rod and the conveying pipe are reciprocated 'by the rotation of a screw threaded pipe.

This invention relates to writing instruments and, more particularly, to a mechanical lead pencil.

In a known mechanical lead pencil the device for expelling the pencil leads requires a pushing rod. The broken leads are propelled, restrained and ejected by means of a slidable pushing rod which is operated by turning the pencil barrel. The barrel turns a screw pipe.

In case the cylindrical guiding pipe for the lead is long, it is projected from the end portion of the metal barrel, i.e., the pipe is longer than the pushing rod, the broken leads may not be ejected entirely from the pencil. In this type of pencil, it is difiicult to modify the structure so that it expels and reciprocates the lead.

It is therefore the main Objective of this invention to provide a mechanical lead pencil having a device for expelling the pencil lead, the device having a construction capable of handling a lengthened pushing length of the pushing rod.

According to the present invention, a lead pencil is provided having a metal tubular body. A cap is provided which may be rotated relative to the body. The cap is turned, i.e., rotated, to cause the lead to be ejected or to place a new lead in the pencil.

The cap is removably connected to a propelling tube which extends into the pencil body. The propelling tube has projections which fit the inside wall of the cap. The propelling tube turns with the cap.

The bottom of the propelling tube is fixed to a short tubular nipple, which is the screw barrel. The screw barrel is fixed to the screw pipe, which has an open helical thread. The turning of the propelling tube turns the screw barrel and thus turns the screw pipe. The screw barrel rotates on the top of a metal piece which is removably connected to the pencil body.

A metal inner tube having a slit along its entire length is fixed in the same metal piece. The inner slit tube is inside the screw pipe and the screw barrel.

A conveyor pipe is positioned within the slit tube. The conveyor pipe has a projection which protrudes through the slit of the inner tube and meshes with the screw pipe thread. When the screw pipe is turned (by turning the cap) the projection and the conveyor tube are moved upward or downward along the axis of the pencil.

A pushing rod having a projection is positioned within the conveyor tube. The projection on the pushing rod protrudes through a slit in the conveyor tube and also protrudes through the slit in the inner tube. This second projection also meshes with the screw threads.

The parts are assembled so that the two projections are separated at some certain distance. When the cap is turned the conveyor tube and the rod move upward and downward together and maintain the same separation. When the conveyor rod reaches its lower end (toward the pen- 3,477,791 Patented Nov. 11, 1969 ICC cils writing point) it stops. The pushing rod, however, may advance more by further turning of the cap and by shortening the distance between the two projections.

For a better understanding of the invenion, as well as furher objectives and features thereof, reference is made to the following detailed description to be read in conjunction with the accompanying drawings, wherein like figures are represented by like reference numerals. In the drawings:

FIG. 1 is a longitudinal sectional view of the mechanical lead pencil showing the device for expelling the leads:

FIG. 2 is a sectional plane view on a line 11-11 of FIG. 1;

FIG. 3 is a sectional plane view on the line IIIIII of FIG. 1;

FIG. 4 is a perspective view of the: pushing rod and holding pipe of the pencil lead; and

FIG. 5 is a sectional plane view showing the direction of the arrow after sectioned on a line IV-IV of FIG. 4, respectively.

Referring now to FIG. 1, the metal body 25 is tubular and has at its lower end an opening. An internal metal piece 1 in the opening has a center hole 2. The metal piece 1 acts as a support for the lead reciprocating mechanism. A first pipe (metal tube) 3 has a longitudinal scored slit 4 along its entire length. The bottom end por tion 5 of slitted pipe 3 fits tightly into the said hole 2 of the metal piece 1.

As shown in FIG. 4, a tubular conveying pipe 8 has a projection 9 on its outside wall at its. approximate central portion. Conveying pipe 8 also has a protuberance 10 with an oval-shaped section below its projection 9. A small slit 11 in pipe 8 has its length equal to the desired length of the movement of the pushing rod 12 in pipe 8, the slit 11 being provided above the projection 9. A second slit 29 in pipe 8 is provided to obtain the springy movement and to form the protuberance 10.

A screw pipe 6 is fixed outside and around the slit pipe 3. A screw barrel 7 is fixed at the bottom end portion of the screw pipe 6. The screw barrel 7 is a small tubular nipple which fits on, and is connected to, the screw pipe 6. The screw barrel is rotatable (along with the screw barrel) on top of the metal piece 1. The inner wall of the screw barrel is unthreaded and forms an unthreaded clearance space below the screw pipe 6. The projection 9 fits and turns within the helical open thread of the screw pipe 6. A clearance is formed between the screw pipe 6 and the longitudinal scored slit 4. The projection 9 and projection 13 both fit within the helical open threads of the screw pipe 6. As seen in FIG. 4, the said projection 13 is inserted into the inner portion of slit 11 of conveying pipe 8 to slide and move. The conveying pipe 8 is assembled within the slit pipe 3. The two projections 9 and 13 protrude through the slit 4 in slit pipe 3 and protrude into the screw threads of screw pipe 6. Two projections 9 and 13 are assembled with sufficient distance between them to eject the lead, the distance between the projections corresponding to a plurality of screw pitches over the whole length of screw pipe 6. In this assembly operation, the slit pipe 3 will be removably connected with the screw pipe 6 by folding the upper portion of the slit pipe 3 toward the outside and using a washer 18 to receive the thrust.

In the preferred embodiment, as shown in FIG. 3, an external hexagonal flange portion of the metal piece 1 is connected with the bottom end of a fixed pencil body 25. A fixing nut 26 is screwed at the lower portion of the metal piece 1 to tightly connect it with the fixed cylindrical body 25. A metal barrel 27 extending outwardly together with the lead guiding tube 28 is removably screwed at the lower portion of the metal piece 1.

In operation, one propels and ejects the lead by turning the cap 24. The cap 24 is separate from the pencil body 25. The cap is connected to a propelling tube 19. In this embodiment, two circular projections 20, 21 tightly, but removably, connect the propelling tube 19 with the metal body 24. Two longitudinal slits 2,2, 23 in tube 19 are provided in its upper portion. The propelling tube 19 is connected, by being squeezed or swaged, on the outside of the barrel portion 7 of the screw pipe 6. The cap turns the propelling tube and the propelling tube turns the screw pipe 6. In this construction, if the user overturns the cap 24, the damage of the respective members is lessened. In case the cap 24 is overturned, the cap cylinder 24 will slip on the propelling tube 19.

The upward and downward movements of the lead conveying pipe 8 are carried out in cooperation with the pushing rod. The said lead conveying pipe 8 is restrained at the bottom end portion of the conveying pipe 8, as shown in FIG. 1, when its protuberance 9 is at the bottom of the screw pipe.

In the assembly operation, when the downward movement of the conveying pipe 8 is limited by the bottom end portion of the conveying pipe and the projection 9 is positioned in a clearance 14 formed by an upper area of the metal piece 1, the bottom portion of screw pipe 6 and inside of the screw barrel 7. The said clearance 14 is formed by assembling a lower protuberance 15 of screw pipe 8 at the scored slits 16 of screw barrel 7. According to this construction, the propelling movement of the screw pipe 6 is smoothly carried out without impediment.

Since a further propelling movement of the screw pipe 6 may be smoothly continued after the lead conveying pipe 8 is positioned at the bottom end portion, the said pushing rod 12 is further advanced and an ejecting movement of the lead 30 is accomplished.

The position as shown in FIG. 1 is the lowest position of the pushing rod 12 which expelled the lead 30. The rod 12, when a new lead is inserted, reciprocates together with the turning of the screw pipe 6. Accordingly, when retrograding after ejecting the lead, at first only the pushing rod 12 will retrograde. In case the projection 13 reaches the top end portion of the closed slit 11 (in the lead conveying pipe 8), i.e., when the said projection 13 returns to its original position, then the said lead conveying pipe 8 is pulled out from the tapered bottom end portion 5 in pipe 3 and is again engaged with the spiral pitch of the screw pipe 6.

In this invention, various changes in the size and shape of the different parts, as well as modifications and alterations, may be made within the scope of the appended claim.

What is claimed is:

1. In a mechanical pencil, an expelling device for the lead, said device consisting of a metal piece having a hole through its central portion, a pipe fitted in the hole of the said metal piece and having a slit substantially along its length, a screw pipe rotatably positioned around the said slit pipe, a conveying pipe for pencil leads reciprocable upward and downward within the said slit pipe, the said conveyor pipe having a projection located in the threaded passage of the said screw pipe and having a longitudinal slit, and a lead pushing rod reciprocal upward and downward in the said conveying pipe, the said rod having a projection within the screw passage of the said screw pipe and projecting from the longitudinal slit of the said slit pipe, wherein said conveying pipe has a protuberance to support the conveyor pipe within the slit pipe and a springy slit is provided at the approximately central portion of the protuberance.

References Cited UNITED STATES PATENTS 1,910,552 5/1933 Lanoie 40164 1,932,371 10/1933 Keeran 40164 2,722,913 11/ 1955 Aversa 40164 2,866,438 12/1958 Schischkow l--64 LAWRENCE CHARLES, Primary Examiner 

